1. Field of the Invention
The present invention relates to a drive joint mechanism designed to couple a drive shaft and a driven shaft in coaxial relation to each other. The present invention also relates to an image forming apparatus using the drive joint mechanism.
2. Description of the Related Art
As a drive joint mechanism for an image forming apparatus, there has been known one type having a structure as shown in FIG. 6 (see, for example, JP 11-043229A: Patent Publication 1). The drive joint mechanism illustrated in FIG. 6 includes a coupling 101 mounted to a drive shaft 100 provided on the side of an apparatus main body of the image forming apparatus, and an engagement pin 103 mounted to a driven shaft 102 provided on the side of a sheet feed cassette which is inserted into the apparatus main body. In a process of assembling this drive joint mechanism, the engagement pin 103 is brought into contact with the coupling 101 in such a manner as to allow the engagement pin 103 to be engaged with an engagement groove 101a of the coupling 101.
With a view to allowing the engagement pin 103 to be engaged with the engagement groove 101a of the coupling 101, the drive joint mechanism disclosed in the Patent Publication 1 is designed such that the coupling 101 is mounted on the drive shaft 100 to be an axially slidably displaceable relative to the drive shaft 100, while being urged against the engagement pin 103 by a coil spring 105 so as to establish the engagement between the engagement pin 103 and the engagement groove 101a along with rotation of the drive shaft 100. This arrangement requires a space for permitting the slide displacement of the coupling 101, and thereby causes a problem about difficulty in facilitating a reduction in size of the drive joint mechanism. Moreover, the need for the coil spring 105 is a negative factor causing an increase in cost and deterioration in assembling efficiency of the drive joint mechanism.